As the development of technology, conventional fluorescent lamps are gradually replaced by LEDs (light emitting diodes) in applications such as LCD backlighting and lighting. In the application of smart LED lighting, a driver is needed to provide a controllable current. Different power supply voltages, such as 3.3V, 5V etc. are also needed to power smart modules (e.g. microcontroller unit (MCU), wireless module R/F, etc.) at different situations.
Conventional two-channel LED drivers typically adopt two power stages: a first stage including a converter (e.g. a flyback converter) to provide two constant voltages, with one voltage driving the LEDs, and the other voltage powering other modules; and a second stage including two step-down converters, to control the current flowing through the LEDs in the two channels, respectively. If one of the LED channels is short, conventional LED driver would shut down the corresponding power stage, to stop supplying power to the open channel.
Monolithic Power Systems Inc. (MPS) provides a different solution for driving two-channel LEDs. It adopts only one power stage, to both drive the two-channels and to power a wireless module. Two dimming signals are provided by the wireless module, with one dimming signal controlling the total luminance of the two-channel LEDs, while the other dimming signal controlling the dimming ratio between the two channels. If one of the channels is short, or both of the two channels are short, how to detect this short condition, and further how to protect the system is a challenge.